[POJ 2891]Strange Way to Express Integers：扩展中国剩余定理

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这里是教程

/*User:SmallLanguage:C++Problem No.:2891*/#include<stdio.h>#include<iostream>#include<iomanip>#include<string.h>#include<algorithm>#include<queue>#include<stack>#include<math.h>#include<map>#define ll long long#define inf 999999999using namespace std;const int M=1005;ll n,c[M],m[M];ll gcd(ll a,ll b){    return b==0?a:gcd(b,a%b);}void exgcd(ll a,ll b,ll &x,ll &y){    if(b==0){        x=1;        y=0;        return;    }    exgcd(b,a%b,y,x);    y-=a/b*x;}ll inv(ll a,ll b){    ll x,y;    exgcd(a,b,x,y);    x=(x%b+b)%b;    if(!x) x+=b;    return x;}int main(){    freopen("data.in","r",stdin);//    ios::sync_with_stdio(false);    while(cin>>n){        bool flag=0;        for(int i=1;i<=n;i++) cin>>m[i]>>c[i];        for(int i=2;i<=n;i++){            ll m1=m[i-1],m2=m[i],c1=c[i-1],c2=c[i];            ll t=gcd(m1,m2);            if((c2-c1)%t){                flag=1;                break;            }            m[i]=m1/t*m2;            c[i]=inv(m1/t,m2/t)*((c2-c1)/t)%(m2/t)*m1+c1;            c[i]=(c[i]%m[i]+m[i])%m[i];        }        if(flag) c[n]=-1;        cout<<c[n]<<endl;    }    return 0;}